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powerpc: Implement GPIO driver for simple memory-mapped banks

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The driver supports very simple GPIO controllers, that is, when a
controller provides just a 'data' register. Such controllers may be
found in various BCSRs (Board's FPGAs used to control board's
switches, LEDs, chip-selects, Ethernet/USB PHY power, etc).

So far we support only 1-byte GPIO banks. Support for other widths may
be implemented when/if needed.

p.s.
To avoid "made up" compatible entries (like compatible = "simple-gpio"),
boards must call simple_gpiochip_init() to pass the compatible string.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
This commit is contained in:
Anton Vorontsov 2008-12-18 19:37:26 +03:00 • committed by Kumar Gala
parent 94409d6e10
commit 3d64de9c50
4 changed files with 179 additions and 0 deletions
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155
arch/powerpc/sysdev/simple_gpio.c Normal file
View file

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/*
* Simple Memory-Mapped GPIOs
*
* Copyright (c) MontaVista Software, Inc. 2008.
*
* Author: Anton Vorontsov <avorontsov@ru.mvista.com>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*/
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/ioport.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/gpio.h>
#include <asm/prom.h>
#include "simple_gpio.h"
struct u8_gpio_chip {
struct of_mm_gpio_chip mm_gc;
spinlock_t lock;
/* shadowed data register to clear/set bits safely */
u8 data;
};
static struct u8_gpio_chip *to_u8_gpio_chip(struct of_mm_gpio_chip *mm_gc)
{
return container_of(mm_gc, struct u8_gpio_chip, mm_gc);
}
static u8 u8_pin2mask(unsigned int pin)
{
return 1 << (8 - 1 - pin);
}
static int u8_gpio_get(struct gpio_chip *gc, unsigned int gpio)
{
struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
return in_8(mm_gc->regs) & u8_pin2mask(gpio);
}
static void u8_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
{
struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);
struct u8_gpio_chip *u8_gc = to_u8_gpio_chip(mm_gc);
unsigned long flags;
spin_lock_irqsave(&u8_gc->lock, flags);
if (val)
u8_gc->data |= u8_pin2mask(gpio);
else
u8_gc->data &= ~u8_pin2mask(gpio);
out_8(mm_gc->regs, u8_gc->data);
spin_unlock_irqrestore(&u8_gc->lock, flags);
}
static int u8_gpio_dir_in(struct gpio_chip *gc, unsigned int gpio)
{
return 0;
}
static int u8_gpio_dir_out(struct gpio_chip *gc, unsigned int gpio, int val)
{
u8_gpio_set(gc, gpio, val);
return 0;
}
static void u8_gpio_save_regs(struct of_mm_gpio_chip *mm_gc)
{
struct u8_gpio_chip *u8_gc = to_u8_gpio_chip(mm_gc);
u8_gc->data = in_8(mm_gc->regs);
}
static int __init u8_simple_gpiochip_add(struct device_node *np)
{
int ret;
struct u8_gpio_chip *u8_gc;
struct of_mm_gpio_chip *mm_gc;
struct of_gpio_chip *of_gc;
struct gpio_chip *gc;
u8_gc = kzalloc(sizeof(*u8_gc), GFP_KERNEL);
if (!u8_gc)
return -ENOMEM;
spin_lock_init(&u8_gc->lock);
mm_gc = &u8_gc->mm_gc;
of_gc = &mm_gc->of_gc;
gc = &of_gc->gc;
mm_gc->save_regs = u8_gpio_save_regs;
of_gc->gpio_cells = 2;
gc->ngpio = 8;
gc->direction_input = u8_gpio_dir_in;
gc->direction_output = u8_gpio_dir_out;
gc->get = u8_gpio_get;
gc->set = u8_gpio_set;
ret = of_mm_gpiochip_add(np, mm_gc);
if (ret)
goto err;
return 0;
err:
kfree(u8_gc);
return ret;
}
void __init simple_gpiochip_init(const char *compatible)
{
struct device_node *np;
for_each_compatible_node(np, NULL, compatible) {
int ret;
struct resource r;
ret = of_address_to_resource(np, 0, &r);
if (ret)
goto err;
switch (resource_size(&r)) {
case 1:
ret = u8_simple_gpiochip_add(np);
if (ret)
goto err;
break;
default:
/*
* Whenever you need support for GPIO bank width > 1,
* please just turn u8_ code into huge macros, and
* construct needed uX_ code with it.
*/
ret = -ENOSYS;
goto err;
}
continue;
err:
pr_err("%s: registration failed, status %d\n",
np->full_name, ret);
}
}